Phytosterols photooxidation in O/W emulsion: Influence of emulsifier composition and interfacial properties

Although phytosterols (PS) showed various excellent health functions, their applications in the food industry were limited by poor water solubility and high oxidation sensitivity. This study investigated the fabrication of phytosterol-enriched emulsions stabilized by different emulsifiers and evaluated the effect of different interfacial layers on the photooxidation of phytosterols and emulsions. The emulsions were prepared with Tween 20, whey protein isolate (WPI), and soy protein isolate (SPI) to achieve interfacial membranes with different properties. The SPI-dextran mixture or dextran-glycated SPI was adopted as the additional emulsifier. Compared with Tween 20, high molecular weight emulsifiers (proteins and their mixtures) exhibited stronger photooxidation stabilities and high viscosity and density of droplet interfacial membrane. The stability of PS emulsions that undergo photooxidation was impacted by the inclusion of these emulsifiers, whereas the extent of phytosterols photooxidation was, from highest to lowest, in the following order: SPI/dextran mixture > glycated SPI mixture > WPI > SPI > Tween 20. The proper SPI concentration (1.5 wt%) showed the highest interface pressure and viscosity and the higher PS stability. Moreover, the higher rheological properties and surface pressure of droplets reveal extra oxidative stability and lower oxidation rate of PS, as well as the formation of additional 7 beta-OH products. This work demonstrates that emulsions may be tuned toward better photooxidation oxidative stability by modifying interface composition and interfacial properties.